from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton
import sys
from PyQt5.QtCore import QSize, Qt


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()

        self.setWindowTitle('My App')

        button = QPushButton('Press Me !!!')

        self.setFixedSize(QSize(400, 300))
        self.setCentralWidget(button)

app = QApplication(sys.argv)

window = MainWindow()
window.show()

app.exec_()
